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From: Jean-Philippe Brucker <jean-philippe@linaro.org>
To: Lu Baolu <baolu.lu@linux.intel.com>
Cc: joro@8bytes.org, will@kernel.org, lorenzo.pieralisi@arm.com,
	robh+dt@kernel.org, guohanjun@huawei.com, sudeep.holla@arm.com,
	rjw@rjwysocki.net, lenb@kernel.org, robin.murphy@arm.com,
	Jonathan.Cameron@huawei.com, eric.auger@redhat.com,
	iommu@lists.linux-foundation.org, devicetree@vger.kernel.org,
	linux-acpi@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	linux-accelerators@lists.ozlabs.org,
	jacob.jun.pan@linux.intel.com, kevin.tian@intel.com,
	vdumpa@nvidia.com, zhangfei.gao@linaro.org,
	shameerali.kolothum.thodi@huawei.com, vivek.gautam@arm.com,
	zhukeqian1@huawei.com, wangzhou1@hisilicon.com,
	Ashok Raj <ashok.raj@intel.com>
Subject: Re: [PATCH v13 06/10] iommu: Add a page fault handler
Date: Tue, 23 Mar 2021 11:51:13 +0100	[thread overview]
Message-ID: <YFnIIYW0aMdGXuS/@myrica> (raw)
In-Reply-To: <15ff4704-0fbd-243f-8e49-a9523ae63ce6@linux.intel.com>

On Wed, Mar 03, 2021 at 01:27:34PM +0800, Lu Baolu wrote:
> I have tested this framework with the Intel VT-d implementation. It
> works as expected. Hence,
> 
> Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
> Tested-by: Lu Baolu <baolu.lu@linux.intel.com>

Thanks!

> One possible future optimization is that we could allow the system
> administrators to choose between handle PRQs in a workqueue or handle
> them synchronously. One research discovered that most of the software
> latency of handling a single page fault exists in the schedule part.
> Hence, synchronous processing will get shorter software latency if PRQs
> are rare and limited.

Yes, the risk is that processing a fault synchronously will take too much
time, leading to PRI queue overflow if the IOMMU keeps receiving page
faults. That's why I opted for the workqueue initially, but it's
definitely something we can tweak

Thanks,
Jean

WARNING: multiple messages have this Message-ID (diff)
From: Jean-Philippe Brucker <jean-philippe@linaro.org>
To: Lu Baolu <baolu.lu@linux.intel.com>
Cc: vivek.gautam@arm.com, guohanjun@huawei.com, will@kernel.org,
	Ashok Raj <ashok.raj@intel.com>,
	linux-acpi@vger.kernel.org, zhangfei.gao@linaro.org,
	lenb@kernel.org, devicetree@vger.kernel.org,
	kevin.tian@intel.com, robh+dt@kernel.org,
	linux-arm-kernel@lists.infradead.org, rjw@rjwysocki.net,
	iommu@lists.linux-foundation.org, sudeep.holla@arm.com,
	robin.murphy@arm.com, linux-accelerators@lists.ozlabs.org
Subject: Re: [PATCH v13 06/10] iommu: Add a page fault handler
Date: Tue, 23 Mar 2021 11:51:13 +0100	[thread overview]
Message-ID: <YFnIIYW0aMdGXuS/@myrica> (raw)
In-Reply-To: <15ff4704-0fbd-243f-8e49-a9523ae63ce6@linux.intel.com>

On Wed, Mar 03, 2021 at 01:27:34PM +0800, Lu Baolu wrote:
> I have tested this framework with the Intel VT-d implementation. It
> works as expected. Hence,
> 
> Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
> Tested-by: Lu Baolu <baolu.lu@linux.intel.com>

Thanks!

> One possible future optimization is that we could allow the system
> administrators to choose between handle PRQs in a workqueue or handle
> them synchronously. One research discovered that most of the software
> latency of handling a single page fault exists in the schedule part.
> Hence, synchronous processing will get shorter software latency if PRQs
> are rare and limited.

Yes, the risk is that processing a fault synchronously will take too much
time, leading to PRI queue overflow if the IOMMU keeps receiving page
faults. That's why I opted for the workqueue initially, but it's
definitely something we can tweak

Thanks,
Jean
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu

WARNING: multiple messages have this Message-ID (diff)
From: Jean-Philippe Brucker <jean-philippe@linaro.org>
To: Lu Baolu <baolu.lu@linux.intel.com>
Cc: vivek.gautam@arm.com, guohanjun@huawei.com, will@kernel.org,
	lorenzo.pieralisi@arm.com, Ashok Raj <ashok.raj@intel.com>,
	zhukeqian1@huawei.com, joro@8bytes.org, wangzhou1@hisilicon.com,
	linux-acpi@vger.kernel.org, zhangfei.gao@linaro.org,
	lenb@kernel.org, devicetree@vger.kernel.org,
	kevin.tian@intel.com, jacob.jun.pan@linux.intel.com,
	eric.auger@redhat.com, robh+dt@kernel.org,
	Jonathan.Cameron@huawei.com,
	linux-arm-kernel@lists.infradead.org, rjw@rjwysocki.net,
	shameerali.kolothum.thodi@huawei.com,
	iommu@lists.linux-foundation.org, sudeep.holla@arm.com,
	robin.murphy@arm.com, linux-accelerators@lists.ozlabs.org
Subject: Re: [PATCH v13 06/10] iommu: Add a page fault handler
Date: Tue, 23 Mar 2021 11:51:13 +0100	[thread overview]
Message-ID: <YFnIIYW0aMdGXuS/@myrica> (raw)
In-Reply-To: <15ff4704-0fbd-243f-8e49-a9523ae63ce6@linux.intel.com>

On Wed, Mar 03, 2021 at 01:27:34PM +0800, Lu Baolu wrote:
> I have tested this framework with the Intel VT-d implementation. It
> works as expected. Hence,
> 
> Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
> Tested-by: Lu Baolu <baolu.lu@linux.intel.com>

Thanks!

> One possible future optimization is that we could allow the system
> administrators to choose between handle PRQs in a workqueue or handle
> them synchronously. One research discovered that most of the software
> latency of handling a single page fault exists in the schedule part.
> Hence, synchronous processing will get shorter software latency if PRQs
> are rare and limited.

Yes, the risk is that processing a fault synchronously will take too much
time, leading to PRI queue overflow if the IOMMU keeps receiving page
faults. That's why I opted for the workqueue initially, but it's
definitely something we can tweak

Thanks,
Jean

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply	other threads:[~2021-03-23 10:52 UTC|newest]

Thread overview: 84+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-02  9:26 [PATCH v13 00/10] iommu: I/O page faults for SMMUv3 Jean-Philippe Brucker
2021-03-02  9:26 ` Jean-Philippe Brucker
2021-03-02  9:26 ` Jean-Philippe Brucker
2021-03-02  9:26 ` [PATCH v13 01/10] iommu: Fix comment for struct iommu_fwspec Jean-Philippe Brucker
2021-03-02  9:26   ` Jean-Philippe Brucker
2021-03-02  9:26   ` Jean-Philippe Brucker
2021-03-25 17:37   ` Will Deacon
2021-03-25 17:37     ` Will Deacon
2021-03-25 17:37     ` Will Deacon
2021-03-02  9:26 ` [PATCH v13 02/10] iommu/arm-smmu-v3: Use device properties for pasid-num-bits Jean-Philippe Brucker
2021-03-02  9:26   ` Jean-Philippe Brucker
2021-03-02  9:26   ` Jean-Philippe Brucker
2021-03-25 17:36   ` Will Deacon
2021-03-25 17:36     ` Will Deacon
2021-03-25 17:36     ` Will Deacon
2021-03-02  9:26 ` [PATCH v13 03/10] iommu: Separate IOMMU_DEV_FEAT_IOPF from IOMMU_DEV_FEAT_SVA Jean-Philippe Brucker
2021-03-02  9:26   ` Jean-Philippe Brucker
2021-03-02  9:26   ` Jean-Philippe Brucker
2021-03-03  5:04   ` Lu Baolu
2021-03-03  5:04     ` Lu Baolu
2021-03-03  5:04     ` Lu Baolu
2021-03-02  9:26 ` [PATCH v13 04/10] iommu/vt-d: Support IOMMU_DEV_FEAT_IOPF Jean-Philippe Brucker
2021-03-02  9:26   ` Jean-Philippe Brucker
2021-03-02  9:26   ` Jean-Philippe Brucker
2021-03-02  9:26 ` [PATCH v13 05/10] uacce: Enable IOMMU_DEV_FEAT_IOPF Jean-Philippe Brucker
2021-03-02  9:26   ` Jean-Philippe Brucker
2021-03-02  9:26   ` Jean-Philippe Brucker
2021-03-02  9:26 ` [PATCH v13 06/10] iommu: Add a page fault handler Jean-Philippe Brucker
2021-03-02  9:26   ` Jean-Philippe Brucker
2021-03-02  9:26   ` Jean-Philippe Brucker
2021-03-02 23:59   ` Jacob Pan
2021-03-02 23:59     ` Jacob Pan
2021-03-02 23:59     ` Jacob Pan
2021-03-23 10:50     ` Jean-Philippe Brucker
2021-03-23 10:50       ` Jean-Philippe Brucker
2021-03-23 10:50       ` Jean-Philippe Brucker
2021-03-03  5:27   ` Lu Baolu
2021-03-03  5:27     ` Lu Baolu
2021-03-03  5:27     ` Lu Baolu
2021-03-23 10:51     ` Jean-Philippe Brucker [this message]
2021-03-23 10:51       ` Jean-Philippe Brucker
2021-03-23 10:51       ` Jean-Philippe Brucker
2021-03-03  5:57   ` Raj, Ashok
2021-03-03  5:57     ` Raj, Ashok
2021-03-03  5:57     ` Raj, Ashok
2021-03-23 10:53     ` Jean-Philippe Brucker
2021-03-23 10:53       ` Jean-Philippe Brucker
2021-03-23 10:53       ` Jean-Philippe Brucker
2021-03-02  9:26 ` [PATCH v13 07/10] iommu/arm-smmu-v3: Maintain a SID->device structure Jean-Philippe Brucker
2021-03-02  9:26   ` Jean-Philippe Brucker
2021-03-02  9:26   ` Jean-Philippe Brucker
2021-03-02 12:24   ` Keqian Zhu
2021-03-02 12:24     ` Keqian Zhu
2021-03-02 12:24     ` Keqian Zhu
2021-03-25 17:48   ` Will Deacon
2021-03-25 17:48     ` Will Deacon
2021-03-25 17:48     ` Will Deacon
2021-03-26  9:49     ` Jean-Philippe Brucker
2021-03-26  9:49       ` Jean-Philippe Brucker
2021-03-26  9:49       ` Jean-Philippe Brucker
2021-03-02  9:26 ` [PATCH v13 08/10] dt-bindings: document stall property for IOMMU masters Jean-Philippe Brucker
2021-03-02  9:26   ` Jean-Philippe Brucker
2021-03-02  9:26   ` Jean-Philippe Brucker
2021-03-02  9:26 ` [PATCH v13 09/10] ACPI/IORT: Enable stall support for platform devices Jean-Philippe Brucker
2021-03-02  9:26   ` Jean-Philippe Brucker
2021-03-02  9:26   ` Jean-Philippe Brucker
2021-03-02  9:26 ` [PATCH v13 10/10] iommu/arm-smmu-v3: Add " Jean-Philippe Brucker
2021-03-02  9:26   ` Jean-Philippe Brucker
2021-03-02  9:26   ` Jean-Philippe Brucker
2021-03-19 17:40   ` Auger Eric
2021-03-19 17:40     ` Auger Eric
2021-03-19 17:40     ` Auger Eric
2021-03-26  9:52   ` Auger Eric
2021-03-26  9:52     ` Auger Eric
2021-03-26  9:52     ` Auger Eric
2021-03-18  0:25 ` [PATCH v13 00/10] iommu: I/O page faults for SMMUv3 Krishna Reddy
2021-03-18  0:25   ` Krishna Reddy
2021-03-18  0:25   ` Krishna Reddy
2021-03-30 17:17 ` Jean-Philippe Brucker
2021-03-30 17:17   ` Jean-Philippe Brucker
2021-03-30 17:17   ` Jean-Philippe Brucker
2021-04-01  8:57   ` Will Deacon
2021-04-01  8:57     ` Will Deacon
2021-04-01  8:57     ` Will Deacon

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